Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
  • B01F23/00—Mixing according to the phases to be mixed, e.g. dispersing or emulsifying
  • B01F23/20—Mixing gases with liquids
  • B01F23/23—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids
  • B01F23/2319—Methods of introducing gases into liquid media
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
  • B01F23/00—Mixing according to the phases to be mixed, e.g. dispersing or emulsifying
  • B01F23/20—Mixing gases with liquids
  • B01F23/23—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids
  • B01F23/237—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids characterised by the physical or chemical properties of gases or vapours introduced in the liquid media
  • B01F23/2376—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids characterised by the physical or chemical properties of gases or vapours introduced in the liquid media characterised by the gas being introduced
  • B01F23/23761—Aerating, i.e. introducing oxygen containing gas in liquids
  • B01F23/237612—Oxygen

Definitions

• German Laid-Open Application DOS. No. 1,593,700 discloses a process in which molecular oxygen is dissolved in cyclohexane by feeding the latter to the top of an absorption column and passing molecular oxygen countercurrent to it.
• hydrocarbons In the presence of molecular oxygen, in contrast to air, hydrocarbons have the disadvantageous property of detonating. This applies in particular at elevated temperatures and when hydrocarbon films form on solid surfaces. Moreover, there is a danger that, when the oxygen feed is interrupted, hydrocarbons will penetrate into the oxygen line and detonate.
• the novel process has the advantages that critical operating states are avoided and, in particular, no sources of danger arise even during exceptional operating conditions, such as failure of the oxygen feed.
• the starting materials used are liquid hydrocarbons, in particular alkanes of 4 to 18 carbon atoms, cycloalkanes containing 5 to 10 carbon atoms in the ring, and alkylaromatics of 7 to 12 carbon atoms. Cycloalkanes having the stated number of carbon atoms, in particular cyclohexane, have become particularly important.
• the molecular oxygen used advantageously contains less than 5, in particular less than 1, % by volume of an inert gas, such as nitrogen, carbon dioxide or a noble gas.
• the dissolution process is carried out in a vertical absorption zone, for example an absorption tower, which advantageously has a length/diameter ratio of from 5:1 to 20:1.
• a layer of water is maintained at the lower end of the absorption zone, this layer advantageously occupying from 10 to 50% of the volume of the absorption zone.
• the layer of water advantageoulsy contains salts, such as alkali metal salts, eg. sodium chloride, sodium sulfate or potassium phosphate.
• the salt content is preferably from 50 to 90% by weight, based on the saturation value.
• surfactants such as cationic, anionic or neutral surfactants. Examples of suitable surfactants are sulfates or phosphates of longchain alcohols.
• a content of from 0.001 to 0.1% by weight of surfactants is sufficient.
• the molecular oxygen is advantageously passed in finely divided form into the layer of water.
• the liquid hydrocarbon is fed into the absorption zone above the layer of water, advantageously directly above this layer.
• the finely divided molecular oxygen rising from the layer of water is passed upward together with the liquid hydrocarbon, with thorough mixing in the absorption zone. Because the molecular oxygen is finely dispersed in the layer of water, buoyancy causes it to pass automatically into the hydrocarbon layer, where it is present in finely divided form. It should be ensured that no cohesive gas phase is formed. This is achieved if the absorption zone is always kept completely full of liquid and a small bleed stream, eg. from 0.005 to 0.1 times the total amount of hydrocarbon fed in, is removed, advantageously at the uppermost end, and stripped with nitrogen. This prevents the formation of a cohesive gas phase.
• the liquid hydrocarbon obtained in this procedure is added to the starting hydrocarbon.
• the absorption zone advantageously has, for example, from 1 to 6 constrictions along its length, in the part in which the liquid hydrocarbon is passed upward together with molecular oxygen.
• baffles are located between the constrictions.
• a plurality of constrictions are arranged in one plane.
• the constrictions are advantageously in the form of nozzle openings so that the rising mixture of hydrocarbons and molecular oxygen reach a flow rate of from 2 to 60 m/s at the nozzle exit. It has also proven advantageous to circulate some of the solution of molecular oxygen in the hydrocarbon.
• the said solution is removed near the upper end of the absorption column in an amont which corresponds to 2-50 times the amount of hydrocarbon fed in, and is recycled to the absorption zone at a point directly above the layer of water.
• the absorption is carried out at from 0° to 50° C.
• the temperature is chosen so that, as far as possible, it is only a few degrees above the melting point of the water or of the hydrocarbon, whichever of the two is the higher.
• the pressure is maintained at from 10 to 100 bar and care is taken to ensure that it corresponds in each case to 1.1-1.5 times the saturation pressure at the particular temperature used.
• the amount of oxygen dissolved in the hydrocarbons is advantageously such that a degree of saturation of from 60 to 90% is achieved under the particular pressure and temperature conditions used.
• solutions of molecular oxygen in liquid hydrocarbons which are obtainable by the process of the invention, are useful for further reaction in the production of oxidation products; for example, cyclohexane solutions containing molecular oxygen are used for the preparation of cyclohexanone and cyclohexanol.

Landscapes

• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Oxygen, Ozone, And Oxides In General (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=6269080

Family Applications (1)

Country Status (4)

Cited By (1)

Citations (3)

Family Cites Families (1)

• 1985
  • 1985-04-25 DE DE19853514924 patent/DE3514924A1/de not_active Withdrawn
• 1986
  • 1986-04-22 DE DE8686105531T patent/DE3680812D1/de not_active Expired - Lifetime
  • 1986-04-22 EP EP86105531A patent/EP0199339B1/de not_active Expired - Lifetime
  • 1986-04-23 US US06/854,917 patent/US4735741A/en not_active Expired - Lifetime
  • 1986-04-23 JP JP61092439A patent/JPS61247603A/ja active Pending

Patent Citations (3)

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